1. Field of the Invention
The disclosed embodiments of the present invention relate to estimating a battery condition of a battery pack, and more particularly, to a battery condition estimating apparatus for estimating a battery condition of a battery pack by solely monitoring one selected battery cell and related method thereof.
2. Description of the Prior Art
A variety of electronic devices such as laptop computers, personal digital assistants, cell phones, etc. may be powered by a battery device. The battery device may employ a rechargeable battery of a variety of types such as a nickel cadmium, nickel metal hydride, or lithium ion. It is desirable for a user to be able to monitor the remaining charge on the battery device to know when recharging of the rechargeable battery is necessary. There are a variety of battery gas gauge techniques known in the art for estimating the remaining capacity of the battery device based on a variety of monitored conditions.
Consider a case where the rechargeable battery includes a battery pack with a plurality of battery cells connected in series. One conventional design is to measure a voltage value of each of the series-connected battery cells, and then determine the remaining battery capacity according to the measured voltage values. However, what the user is concerned about is the remaining capacity of the whole battery pack rather than the remaining capacity of each battery cell. Beside, as the battery cells included in the battery pack are connected in series, the remaining capacity of the battery pack is dominated by the remaining capacity of the worst battery cell. Hence, measuring voltage values of all series-connected battery cells is not an efficient way of determining the remaining capacity of the battery pack.
Another conventional design is to measure an average voltage value of the series-connected battery cells, and then determine the remaining battery capacity according to the measured average voltage value. As mentioned above, the remaining capacity of the battery pack is dominated by the remaining capacity of the worst battery cell. The determined remaining battery capacity is less accurate due to the fact that the measured average voltage value is unable to accurately reflect the actual condition of the worst battery cell.
Thus, there is a need for an innovative design which is capable of efficiently and accurately estimating a battery condition of a battery pack having series-connected battery cells included therein.